We have now reached the last great diamond which it is our purpose to chronicle, and it is hoped that the reader has become sufficiently interested in these sparkling pebbles to bear with equanimity a few technical details concerning their nature and the processes which they undergo before becoming ornaments for the crowns of kings or the brooches of queens. [Illustration: DIAMOND IN THE ROUGH.] That the diamond depends for its beauty almost entirely upon the labor of man is sufficiently known. The rough diamond is seldom a beautiful object, being usually coated with a greenish film which gives it the look of an ordinary pebble. It requires the eye of an adept to recognize any potentiality of sparkle in so dull a lump. The ordinary rock-crystal is infinitely more beautiful until the royal gem has been transformed by human skill. But after the touch of the magic wheel there is no substance which can compare with the diamond for luster, brilliancy and iridescence. Certain Indian diamonds finished by the hand of Nature and known as "Naifes," are an exception to the rule that rough diamonds are dull looking. They are seldom or never found now, but were greatly prized by the natives in olden times and considered superior to the artificially polished stone. They were octahedral in form, with polished facets. The primary crystalline form of the diamond is the octahedron, or a figure of eight sides; but it by no means confines itself to this form alone. It sometimes assumes twelve-sided shapes, or is merely a cube, or yet again variations of these figures. The atoms composing the diamond tend to place themselves in layers, and the discovery of this fact facilitated the cutting of the stone, as by finding the grain a skillful manipulator was able to cleave off protuberances at a blow.